Known in the art is an internal combustion engine which comprises a delivery pipe for distributing fuel to fuel injectors and a high pressure pump for pumping high pressure fuel to the inside of the delivery pipe, wherein the fuel pressure in the delivery pipe is made to become a target fuel pressure by control of a fuel pumping period of the high pressure pump and wherein the fuel injection period is set from the fuel pressure in the delivery pipe before the start of fuel injection and the fuel injection amount determined by the operating state of the engine (see PTL 1). In this internal combustion engine, while fuel is being sent from the high pressure pump to the inside of the delivery pipe, the fuel pressure in the delivery pipe changes, therefore if the fuel pumping time period of the high pressure pump and the fuel injection period overlap, error occurs between the amount of fuel which is actually injected from the fuel injector and the fuel injection amount determined from the operating state of the engine.
Therefore, in this internal combustion engine, when the fuel pumping time period of the high pressure pump and the fuel injection period overlap, the fuel injection period is reset right before or right after the fuel pumping time period so that the overlapping fuel pumping time period of the high pressure pump and the fuel injection period is eliminated or becomes smaller. Further, if resetting the fuel injection period causes error to occur with respect to the fuel injection amount determined from the operating state of the engine, the fuel injection period is adjusted so that error no longer occurs.
On the other hand, known in the art is an internal combustion engine which arranges an NOX removing catalyst in an exhaust passage, arranges a reducing agent feed valve for feeding a reducing agent upstream of the NOX removing catalyst in the engine exhaust passage, making the NOX exhausted from the engine when fuel is being burned under a lean air-fuel ratio be stored in the NOX removing catalyst, and, when the air-fuel ratio of the exhaust gas flowing into the NOX removing catalyst should be made rich so as to release the stored NOX from the NOX removing catalyst, combustion gas of a rich air-fuel ratio is generated in the combustion chamber or a reducing agent is injected from the reducing agent feed valve in accordance with the operating state of the engine (see PTL 2). In this internal combustion engine, when the air-fuel ratio of the combustion gas in the combustion chamber is switched from lean to rich and the air-fuel ratio of the combustion gas is made rich and the air-fuel ratio of the combustion gas is switched from rich to lean, a large amount of soot is generated. This large amount of generated soot causes the danger of the nozzle holes of the reducing agent feed valve being clogged. Therefore, in this internal combustion engine, in the period from when rich air-fuel ratio fuel is burned to when the next rich air-fuel ratio fuel is burned, the reducing agent feed valve is made to inject a small amount of reducing agent to blow off the soot which is deposited at the nozzle holes and thereby prevent the nozzle holes of the reducing agent feed valve from being clogged.